三段式高压加热器管束流体弹性失稳临界流速的计算

Calculation on Critical Flow Velocity for Fluid Elastic Instability of Tube Bundle in High Pressure Heater with Three Segments

流体弹性失稳是管壳式热交换器流致振动失效形式之一,导致换热管磨损甚至断裂。管壳式热交换器标准(GB151-1999)中以管束振动的基频作为确定流体弹性失稳临界流速的依据,在结构形式复杂流速不均匀的新型三段式高压加热器设计方面存在应用瓶颈。本文针对三段式高压加热器的结构特点和工作原理,对流速沿整体管束分布作了分段均匀化处理,给出了三段式高压加热器管束流体弹性失稳临界流速的计算方法。计算结果表明,三段式高压加热器的临界流速并非发生在通常人们所认为的最小固有频率处,它不仅与换热管的固有频率有关,而且与振型有关。

Fluid elastic instability induced by the interaction of fluid and tube bundle is one of the serious failure styles in tubular heat exchangers, which leads to the tube＇s wearing and rupture. Regarding to the determination on critical flow velocity for fluid elastic instability, the National Standard （GB151-1999） provides the method based on the first vibration frequency. However this method encounters the application bottleneck on the design of the new type of high pressure heater with three segments during its complicated structure and flow field. Based on the structural specialty and working principle of a high pressure heater with three segments, the critical flow velocity for fluid elastic instability induced by the interaction of fluid and tube bundle was calculated. The primary consideration in the calculation is the non-uniform distribution of the flow velocity along the tube in different segment. The calculated result shows that the critical flow velocity does not occurred at the first vibration frequency of the tube and it is determined by both the vibration frequency and the mode shape distribution on the three segments.